A novel synthesis of Fe₂P-LiFePO₄ composites for Li-ion batteries

Fe₂P-LiFePO₄ composites were synthesized by a novel method consisting of co-precipitation modified with in situ polyacrylamide (PAM) formation. Simultaneous thermogravimetric-differential scanning calorimetric analysis indicated that the in situ PAM precursor exhibited a moderate continuous weight loss rather than a sharp mass loss process. The best Fe ₂P-LiFePO₄ composite was obtained from 14 wt% in situ PAM precursor under a sintering temperature of 750 °C for 20 h, which delivered a discharge capacity of 131 mAh g^-1 at a rate of C/5 and 110 mAh g^-1 at 1 C and sustained 30 cycles with almost no capacity fading. The relatively good electrochemical performance originates mainly from the well-mixed gelation precursor and conductive Fe₂P phase with better electronic conductivity. This novel method verified that the electrochemical performance was improved compared to the conventional LiFePO₄ without in situ PAM. It can be anticipated that the same process should be readily extendable to other olivines, such as LiMnPO₄ and LiCoPO₄, and also to other phosphates.